WO 2013/139685 A1 relates to a valve for an inhalation device comprising a base in the form of a ring defining a central opening, as well as an upper surface and a lower surface, both of which are planar and converge toward each other from the base in the direction opposite said base, wherein the upper and lower surfaces together form an angle of at least 60°, and the free edges thereof define a slit which is open when the valve is at rest.
WO 2010/107723 A2 provides apparatus featuring a check valve featuring a duckbill valve configured to provide fluid and particulate; and an insert having a base portion configured to seat the insert inside the duckbill valve, and a W-shaped portion configured with an opening to pass the fluid and particulate through the duckbill valve and also configured to provide support for walls of the duckbill valve in response to back pressure caused by the fluid and particulate.
US 2004/265523 A1 discloses a bonding structure of check-valves to a fluid container and a production apparatus of fluid container which is capable of reliably keeping the expansion of the fluid container without any fluid leakage after inflating the fluid container. As the check-valve is bonded to only one of thermoplastic container films, the check-valve is fixed to one of the container films, thereby preventing the reverse flow by tightly closing the check valve. As a result, the expansion of the fluid container is reliably maintained after the fluid container is inflated. The manufacturing apparatus includes an up-down roller controller which precisely positions the film to form the check valve. As a result, the manufacturing apparatus can produce the fluid container having the reliable check valves.
US 2012/085958 A1 discloses a plastic formed inflation mouth structure comprising a plastic formed body which is integrally formed with an inflation mouth by plastic injection molding. The inflation mouth includes an inflation apparatus passage and a restoration unit that are integrally formed. The inflation apparatus passage unit is formed with a notch for passage of an inflation apparatus to perform the inflation or deflation. The restoration unit applies an elastic restoration force onto the notch to make the notch assuredly enclose the inflation apparatus during the inflation and ensure a high airtightness when inflation is stopped.
Valves made of rubber, in particular, made of liquid silicone rubber (LSR), with slit openings are used in beverage feeding appliances, in order to control the flow of the beverage. The slit valves can be produced by liquid injection molding (LIM) followed by a slitting process for generating the slit in the respective valve. However, the macromolecules and atoms in the walls on each side of the slit have the tendency to bond again together, which leads to a sticking closing the slit. The valve may not open anymore when there is a pressure difference between the two sides of the valve, i.e. the valve function may fail. It is common practice to apply a slit valve as an air valve and drink valve in drinking appliance for children, such as baby bottles and spout cup. If the valve functions fails, the child cannot suck liquid from the drinking appliance due to the underpressure in the drinking appliance no longer being normalised. In order to crack the slit open, mechanical stress needs to be manually applied in the normal direction of the slit. This operation requires at least introducing a foreign object in the drinking container, such as a hand or a pin. This is not hygienic and may become infected with bacteria. Furthermore, this manual operation is in general too complex for common users and it results in high failure rates of products containing the valves with the slit openings.